Jill T. Oberski

Why ants? Why the “pyramid ants”?

Ants are everywhere—there are over 14,000 known species and an estimated 22 quadrillion individuals on Earth! They’re the most species-rich and ecologically important social insects in the world. Yet, surprisingly, scientists are still learning a lot about them.

I study a group of ants called “pyramid ants” or “cone ants,” in the genus Dorymyrmex. They get their name from the little pointy cone they have on their back—something that all Dorymyrmex species have in common. In some species it’s more like a spine.

Pyramid ants are most common in dry, open places like deserts, grasslands, and even roadsides—landscapes that might look barren at first glance, but are full of hidden biodiversity. Unlike tropical rainforest ants, desert and grassland ants often haven’t been studied as closely, even though they play just as important a role in their ecosystems.

Social life of ants

Ants live in colonies made up of:

• Queens, who lay eggs
• Workers, all sisters who do the labor
• Males, who reproduce and then die shortly after

Each colony acts like one big, complex organism, sometimes called a “superorganism.” In other words, the colony works together so closely that scientists sometimes compare it to a single animal with specialized body parts. Studying social insects like ants helps us understand how cooperation evolves.

Sneaky social parasites

Some Dorymyrmex ants are social parasites. That means a queen from one species can sneak into the nest of another species, kill the host queen, and trick the workers into raising her young instead. It’s a fascinating example of how competition can evolve in a cooperative system—and we’re still figuring out how they pull it off.

This picture shows a queen of Dorymyrmex reginicula, which is a temporary social parasite of species like Dorymyrmex bureni.

Why taxonomy matters

Before we can study where ants live, how they behave, or how they evolved, we have to know what (or who) we’re looking at. That’s where taxonomy—the science of naming and identifying species—comes in.

In North America, there are 15 recognized Dorymyrmex species, but ant scientists (called myrmecologists) including myself have found there are more hiding in plain sight. Many are hard to tell apart, and that’s why I’m working on describing new species and clarifying the ones we already know.

There are still animals new to science in our own backyards—and pyramid ants are just one example!

Dorymyrmex, the “pyramid ants”

Ants are the world’s most species-rich, abundant, and biologically diverse social insects. There are over 14,000 species and 22 quadrillion individuals (!) and they are extremely important for ecosystems, but many groups are still poorly known, even to myrmecologists (ant scientists). In particular, ants are important in dry habitats like deserts and grasslands, which might look biologically “empty” but are buzzing with life if you look closely. These ants often receive less attention than ants from tropical rainforests, but they are equally important. This is true for my study group, the “pyramid ants” or “cone ants”: genus Dorymyrmex.

They get their name from the little pointy cone they have on their back—something that all Dorymyrmex species have in common, although in some species it’s more like a spine.

Range: North, Central, and South America, plus the Caribbean

Habitat: Pyramid ants are extremely common in open habitats like deserts, roadsides, and grasslands, but not in places like tropical rainforests—so although rainforests are extremely diverse in general, they’re not diverse at all for the pyramid ants. Each species has its own habitat preferences, but there are often multiple Dorymyrmex species living in the same place.

Diet: These ants are generalists who will eat pretty much anything, including scavenging dead organisms, and they are sometimes known to take care of, and protect, aphids or other bugs just like farmers with a herd of cattle. The comparison stops there, though… the bugs’ part of the bargain is that they offer the ants their sugary waste, called “honeydew”, to eat. 💩 (It’s mutually beneficial.)

Taxonomy: If we want to study things like behavior, social systems, or geographic ranges (biogeography), it’s critical that we understand what species we’re looking at. The foundation for all this research is accurate taxonomy, and ideally taxonomy based on evolution. This is why I’m working on discovering new species and better defining the species we already know about—because there are animals new to science in our very backyards.

To quote Mark Deyrup (2017), “Dorymyrmex provides enough taxonomic and biogeographical puzzles to keep myrmecologists [ant scientists] happily engaged for decades.” I plan to put that to the test. 🙂

Findings

1. Taxonomy
2. Evolution
3. Biogeography
4. Social parasitism

I. Taxonomy: Combining classical and cutting-edge

Since they were first discovered, the pyramid ants were classified based on their appearance. Sometimes scientists also recorded useful natural history information like nest type and habitat. However, Dorymyrmex species are very hard to tell apart, especially in North America, so this taxonomy has always been quite messy and researchers have been uncertain about what species they are observing.

Luckily, modern taxonomy has the help of genetic data, so I have sequenced the DNA of hundreds of pyramid ant specimens. By analyzing the sequences, I built an evolutionary tree showing the relationships between Dorymyrmex species, and I found there are four major branches (species groups). Throughout history, entomologists developed different versions of this classification. My DNA sequencing results prove that some of these historical groupings were correct—and some were way off.

In order to do high-quality taxonomy, it’s important to consider multiple forms of evidence. Do the species look different? Do they mate at different times of the year? Do they make different kinds of nests? Thinking about what constitutes a “species” from multiple angles helps us understand diversity most accurately. It’s also important for conservation, because species and habitats need to be recognized before they can be preserved.

Until now, scientists only knew about 15 species of Dorymyrmex in North America. By using my evolutionary tree as a guide, and measuring differences in species appearances (= morphology) and nesting habits, I found there are actually at least 27 species.

It is also becoming clear that many more species await discovery and description, particularly in underexplored regions like the Chihuahuan desert. Currently, I’m working to describe these new species in collaboration with other field scientists and researchers.

II. Evolution and genetics

The pyramid ants can show us how evolution works at every biological scale: from molecules (DNA), to the individual ant, to the colony, to the local population, to regional and global distributions.

On the local end of this scale, I discovered that Dorymyrmex species are rapidly evolving. Because they are so young, regional populations might still be interbreeding, and in the fuzzy area between population or species status. For now, these can be called species complexes, and I’m working to analyze their genetic data on a finer scale to learn how new species are emerging.

At the global scale, I found that Dorymyrmex started to diversify when the Andes mountains were created. That process changed the climate across all of South America, and with it, the communities of plants, animals, and fungi. As South America dried out, Dorymyrmex developed cool features like a long psammophore, a basket of hairs on the underside of the head, to assist in carrying difficult loads like grains of sand. This is especially useful for building nests in a desert environment.

III. Biogeography

I find it fascinating to learn about the geographic ranges of species and how they have moved across the planet over time. Dorymyrmex ants are good at relocating over distances because the queens and males have wings, but they show an interesting pattern. Instead of being diverse in tropical forests, they are most common and diverse in dry places. These locations are generally north and south of the tropics. So how do ants migrate between the two areas if they cannot live in the middle?

1. Dorymyrmex are drawn to resource-poor environments like deserts… and therefore also sandy beaches. They are happy to live on (and disperse via!) beaches, which are convenient corridors on the coast, even when inland environments may be more forested and humid.
2. About 8 million years ago (Mya), Dorymyrmex ants traveled from South America to North America. Traditional estimates date the closure of the Isthmus of Panama at 3 Mya, but many trans-isthmus migrations apparently happened earlier. Thus, Dorymyrmex adds to the evidence that the connection between North and South America might be older than scientists have assumed.

IV. Social insects

Dorymyrmex ants are an interesting system for studying social insect biology. Like honeybees, they live in cooperative colonies with a queen (sometimes multiple queens) and many workers. However, some Dorymyrmex species are social parasites of other species, meaning that although ants are cooperative with their nestmates, they can have extreme conflict with other nests—either nests of the same species or a different species.

The parasite queen invades the nest of a host species, kills the host queen, and chemically tricks the host workers into taking care of her own offspring. We still don’t quite understand how they do this, but it’s very interesting how competition can evolve in cooperative systems. With collaborators, I’m working up a study of how social parasitism has evolved in Dorymyrmex.

Introduction

Since the days of Charles Darwin and Alfred Russel Wallace, Western explorers and scientists have been trying to unravel the intertwined mysteries of natural history, morphological evolution, speciation, and biogeography. Over a century later, systematists are still grappling with many of these same questions: Why do we see discrepancies in patterns of biodiversity? How do social insect societies evolve? And—the eternal question—how do we delineate species? Studying taxa that thrive in arid environments may reveal how a changing landscape, such as the desertification spurred on by human-induced climate change, prompts animal species to adapt, diversify, and expand their geographic range. My research on arid-adapted Dorymyrmex ants spans the field of systematics, integrating cutting-edge genome sequencing technologies, studies of phylogeny and evolutionary patterns, and underappreciated basic research in a classical sense: species discovery and description.

Ants (Hymenoptera: Formicidae) are the world’s most species-rich, abundant, and biologically diverse social insects, with over 14,000 species and 22 quadrillion individuals, yet many lineages remain disproportionately understudied. Additionally, it is well established that in arid zones, ants constitute an essential group of animals in terms of abundance, biomass, and nutrient turnover—yet they are relatively neglected by science in comparison to their counterparts in the wet tropics. This is certainly true of the “pyramid ants” or “cone ants,” genus Dorymyrmex Mayr 1866, and, in particular, the Nearctic representatives, which are notorious for their morphological similarity and cryptic diversity—indeed, while there are 15 valid species in North America (as of March 2025), the actual number has long been acknowledged to exceed this estimate.

Dorymyrmex ants are common and conspicuous in deserts, roadsides, and grasslands across the Americas. Because of their habitat preferences, global collection records of Dorymyrmex show an intriguing “amphitropical” or “inverse” latitudinal gradient in contrast to the canonical pattern of greater species richness in the tropics. Inter-species interactions in Dorymyrmex are complex as well; social parasitism has evolved several times, suggesting competition and coevolution between and even within species. Their wide array of social and ecological traits, coupled with their challenging cryptic diversity, makes Dorymyrmex ants an opportune system for studying how different drivers of diversification and speciation interact.

However, to have any biological significance, these studies must rely on firm species definitions. Thus, to address this baseline need and usher Dorymyrmex into the age of molecular phylogenetics, my doctoral work examined the genus using ultraconserved element (UCE) sequencing and established Dorymyrmex ants as a new model system of social insect evolution (Oberski 2022). As a result of this work, I discovered four major clades that differ greatly in age, species richness, degree of morphological variation, and global distribution. In other words, evolution has unfolded unevenly across the genus, suggesting that different processes are jointly driving the evolution of the system. As suggested by Mark Deyrup (2017), “Dorymyrmex provides enough taxonomic and biogeographical puzzles to keep myrmecologists happily engaged for decades.”

Taxonomy: Bridging classical and cutting-edge

Prior to my work, all valid Dorymyrmex taxonomy was based purely on morphology and scant natural history data, taking no consideration of shared ancestry. To usher Dorymyrmex into the age of modern molecular systematics, I performed ultraconserved element (UCE)-based targeted genomics, enriching thousands of loci, to establish a backbone phylogeny for the genus (Oberski 2022; Oberski 2025). Four major monophyletic clades have emerged robustly, representing major lineages (species groups) that have been independently evolving for millions of years. These lineages in fact correspond to former genus boundaries demarcated by morphology, corroborating the work of traditional taxonomy performed centuries and decades ago.

Integrative taxonomy. I am a strong proponent of the integrative, cohesive taxonomic approach. By pulling phylogenetic, morphological, and ecological evidence together, the species that are consistently recovered across methods reveal where populations have become isolated and species have begun to diverge in genome, phenome, and life history. This comprehensive approach not only enhances our understanding of biodiversity, but also underpins active studies in behavior, chemical ecology, and physiology (e.g., Godfrey, Oberski, et al. 2021) and informs conservation strategies, as recognizing endemic lineages is crucial for preserving biodiversity in the face of environmental change.

Undescribed biodiversity. The 15 valid Dorymyrmex species in North America are an incomplete estimate of the diversity present. Thanks to the backbone established with phylogenomics, and supported by classical morphometric measurements, I found there are at least 27 Nearctic species of Dorymyrmex that are difficult, but no longer impossible, to differentiate (taxonomic revision in prep!). This updated taxonomy additionally suggests that many more species await discovery and description, particularly in underexplored regions like the Chihuahuan desert.

Outlook. I am currently preparing this partial taxonomic revision and collaborating with other field scientists and ant natural history experts to integrate ecological data with my genetic findings, enhancing our insights into how environmental factors influence evolutionary processes—and also leveraging the power of multiple generations of myrmecological knowledge.

Evolution and population genetics

From alleles to colonies and populations, to social interactions, ecological preferences, and regional ranges, Dorymyrmex ants are an ideal system to investigate the patterns and processes of evolution across biological scales.

Global-scale, ancient macroevolution. I demonstrated the earliest diversification of South American Dorymyrmex into species groups was favored by major climatic and geological changes that occurred throughout the mid- to late Tertiary period and further driven by the vegetation shifts that accompanied them (Oberski 2025). Climatic cooling and progressive aridification created the South American deserts, grasslands, and scrublands, driving the diversification of bizarre desert specialists with derived morphologies (the Dorymyrmex flavescens and D. tener species groups) as well as more generalist lineages (the D. wolffhuegeli and D. pyramicus species groups). One such derived feature is an expanded psammophore, a basket of hairs on the underside of the head, to assist in carrying larger or multiple loads like grains of sand, enhancing foraging and nest-building efficiency in desert environments—so these morphological adaptations show a complex interplay between ecology and evolution.

Rapid, recent, and ongoing evolution. Additionally during my doctoral work, I demonstrated Dorymyrmex species (and complexes) reflect current ecological dynamics that may further influence their evolutionary trajectories. Namely, Dorymyrmex ants in the D. pyramicus species group are undergoing a rapid radiation indicative of ongoing (incipient) speciation—that is, blurring the lines between species and populations and showing evolution happening in real time. This phenomenon suggests that the species complexes I have identified in my taxonomic revision are not static entities but are experiencing ongoing gene flow.

Outlook. To investigate these population genetic dynamics, I am currently working to analyze genetic data below the species level, allowing for a deeper understanding of the mechanisms driving speciation and adaptation within Dorymyrmex populations.

Biogeography

Ancient historical biogeography has been my primary fascination since my first research experiences with Gondwana-distributed arachnids (Oberski et al. 2018). In Dorymyrmex, the intriguing pan-American “amphitropical” distribution is the result of a South American origin, followed by dispersal northward into Central America, North America, and even the Caribbean islands (Oberski 2022). This pattern Iikewise reveals historical events of universal interest.

Isthmus of Panama. Namely, the Dorymyrmex phylogeny corroborates evidence indicating an earlier, more complex history for the Isthmus of Panama (Oberski 2025). Traditionally, the total closure of the isthmus and the start of the Great American Biotic Interchange (GABI) has been estimated at 3 Ma, but a growing body of evidence suggests that the completion of the isthmus was an older, more gradual process. Divergence dating analyses indicate that Dorymyrmex intercontinental dispersal occurred around 10–6 Ma, supporting these findings of early migrations and a temporary, shifting archipelago. Moreover, Dorymyrmex ants could have used sandy beaches as corridors for dispersal in otherwise humid forested regions—a potential link between the (otherwise disjunct) suitable, resource-poor habitats north and south of the tropics.

Outlook. Between 12–4.5 Ma, the Andes experienced tectonic uplift and Dorymyrmex populations were divided. I hope to investigate the effects of vicariance vs. dispersal during this period and potentially gain insight into the formation of the Atacama and Patagonian deserts. I am also interested in pursuing phylogeographical studies targeting the recent biogeography of Dorymyrmex in North America.

Social insects

Dorymyrmex ants are a fitting system to study the nuances of social insect biology. Like all ants, they are eusocial, i.e., generally living in colonies with reproductive division of labor (queens/workers), overlapping generations, and collaborative brood care. Social insect systems have fascinating implications for the evolutionary process and thus make an excellent “playground” for understanding relatedness, behavior, superorganismality, and the mechanisms of genetic inheritance. 

Implications for evolution. Due to their haploid father and diploid mother, worker ants are more closely related to their sisters (sharing 75% of their genes) than to their own potential offspring. This genetic system is thought to promote the evolution of altruistic behaviors in female workers. Reproductive division of labor also means that the colony is the operational evolutionary unit rather than the individual. Colony characteristics like number of workers, number of queens, and nest structure are often heritable, rather than purely environmental. Even social behavior and sensory anatomy and physiology may relate to colony size (Godfrey, Oberski, et al. 2021).

Implications for taxonomy. Eusociality directly impacts Dorymyrmex taxonomy: species are often indistinguishable using the worker caste, but reproductive castes may shed light on identities since they possess the physical machinery relevant to reproductive isolation. Unfortunately, males and queens are usually short-lived or deeply underground, respectively.

Social parasitism. Social parasitism seems to have evolved several times in Dorymyrmex, even between distantly related species in the genus—in contrast with Emery’s rule, which purports that social parasites and their hosts are each other’s closest relatives. Parasitic behaviors change the demographics of the host colony over time and offer an interesting perspective into how cooperation can lead to exploitation.

Outlook. Together with collaborators, I have active lines of research A) incorporating reproductive castes into my Dorymyrmex taxonomic framework and B) exploring the evolution of social parasitism within the genus.

Selected References (some used above, some just interesting):

• Bacon, C. D., Silvestro, D., Jaramillo, C., Smith, B. T., Chakrabarty, P., & Antonelli, A. (2015). Biological evidence supports an early and complex emergence of the Isthmus of Panama. Proceedings of the National Academy of Sciences, 112(19), 6110–6115. https://doi.org/10.1073/pnas.1423853112
• Deyrup, M. (2017). Ants of Florida. Identification and natural history. CRC Press (Taylor & Francis Group).
• Fisher, B. L., & Cover, S. P. (2007). Ants of North America: A guide to the genera (p. xiv + 194 pp.). University of California Press.
• Godfrey, R. K., Oberski, J. T., Allmark, T., Givens, C., Hernandez-Rivera, J., & Gronenberg, W. (2021). Olfactory System Morphology Suggests Colony Size Drives Trait Evolution in Odorous Ants (Formicidae: Dolichoderinae). Frontiers in Ecology and Evolution, 9, 733023. https://doi.org/10.3389/fevo.2021.733023
• Jay, K., Popkin-Hall, Z., Coblens, M., Oberski, J., Sharma, P., & Boyer, S. (2016). New species of Austropurcellia, cryptic short-range endemic mite harvestmen (Arachnida, Opiliones, Cyphophthalmi) from Australia’s Wet Tropics biodiversity hotspot. ZooKeys, 586, 37–93. https://doi.org/10.3897/zookeys.586.6774
• Lieberman, Z. E., Billen, J., van de Kamp, T., & Boudinot, B. E. (2022). The ant abdomen: The skeletomuscular and soft tissue anatomy of Amblyopone australis workers (Hymenoptera: Formicidae). Journal of Morphology, 283(6), 693–770. https://doi.org/10.1002/jmor.21471
• MacKay, W. P. (1991). The role of ants and termites in desert communities. In G. A. Polis (Ed.), The Ecology of Desert Communities (pp. 113–150). University of Arizona Press.
• Mayr, G. L. (1866). Myrmecologische Beiträge. Sitzungsbericht Der Kaiserlichen Akademie Der Wissenschaften in Wien. Mathematisch-Naturwissenschaftliche Classe. Abteilung I, 53, 484–517.
• Oberski, J. T. (2022). First phylogenomic assessment of the amphitropical New World ant genus Dorymyrmex (Hymenoptera: Formicidae), a longstanding taxonomic puzzle. Insect Systematics and Diversity, 6(1), 8. https://doi.org/10.1093/isd/ixab022
• Oberski, J. T. (2025). UCE phylogenomics illuminate the evolution and biography of Dorymyrmex pyramid ants. Syst. Entomol. https://doi.org/10.1111/syen.12658
• Oberski, J.T., Z.H. Griebenow, R.M.M. Adams, A. Andersen, J. Andrade-Silva, P. Barden, M. Borowiec, S. Brady, S. Csősz, A.M. Dias, R.K.S. Dias, R.M. Feitosa, F. Fernandez, A. Casadei-Ferreira, B.L. Fisher, D.E.M. General, K. Gomez, M. Janda, A. Khalife, N. Ladino, Z. Lieberman, M. Menchetti, L. Pires do Prado, R.S. Probst, A. Punnath, A. Richter, R.R. Silva, S. Salata, A.F. Sánchez-Restrepo, E. Schifani, T.R. Schultz, J. Sosa-Calvo, M.C. Tocora, M.A. Ulysséa, W. Wang, J. Williams, G.P. Camacho, B.E. Boudinot. (in press). Ant Systematics: Past, Present and Future. Insect Systematics and Diversity.
• Oberski, J. T., Sharma, P. P., Jay, K. R., Coblens, M. J., Lemon, K. A., Johnson, J. E., & Boyer, S. L. (2018). A dated molecular phylogeny of mite harvestmen (Arachnida: Opiliones: Cyphophthalmi) elucidates ancient diversification dynamics in the Australian Wet Tropics. Molecular Phylogenetics and Evolution, 127, 813–822. https://doi.org/10.1016/j.ympev.2018.06.029
• Rojas, P., & Fragoso, C. (2000). Composition, diversity, and distribution of a Chihuahuan Desert ant community (Mapimı́, México). Journal of Arid Environments, 44(2), 213–227. https://doi.org/10.1006/jare.1999.0583
• Schultheiss, P., Nooten, S. S., Wang, R., Wong, M. K. L., Brassard, F., & Guénard, B. (2022). The abundance, biomass, and distribution of ants on Earth. Proceedings of the National Academy of Sciences, 119(40), e2201550119. https://doi.org/10.1073/pnas.2201550119
• Smocovitis, V. B. (1992). Unifying biology: The evolutionary synthesis and evolutionary biology. Journal of the History of Biology, 25(1), 1–65. https://doi.org/10.1007/BF01947504
• Snelling, R. R. (1995). Systematics of Nearctic ants of the genus Dorymyrmex (Hymenoptera: Formicidae). Contributions in Science (Los Angeles), 454, 1–14.
• Stehli, F. G., & Webb, S. D. (Eds.). (1985). The Great American Biotic Interchange. Plenum Press.
• Trager, J. C. (1988). A revision of Conomyrma (Hymenoptera: Formicidae) from the southeastern United States, especially Florida, with keys to the species. The Florida Entomologist, 71(1), 11–29. https://doi.org/10.2307/3494888

General

• AntWiki 🐜
• The Myrmecological News Blog, which has great reviews, summaries, and interviews about recently published articles in the journal Myrmecological News.

* For the literature I have included DOI links, which should give you access on university / library internet connections, but let me know if you need a PDF copy.

Scientific Literature ^

• Axelrod, D.I. 1985. Rise of the grassland biome, central North America. The Botanical Review 51: 163–201. https://doi.org/10.1007/BF02861083
• Hewitt, G. 2000. The genetic legacy of the Quaternary ice ages. Nature 405: 907–913. https://doi.org/10.1038/35016000
• Oberski, J. T. (2022). First phylogenomic assessment of the amphitropical New World ant genus Dorymyrmex (Hymenoptera: Formicidae), a longstanding taxonomic puzzle. Insect Systematics and Diversity, 6(1), 8. https://doi.org/10.1093/isd/ixab022
• Oberski, J. T. (2025). UCE phylogenomics illuminate the evolution and biography of Dorymyrmex pyramid ants. Syst. Entomol. https://doi.org/10.1111/syen.12658
• Oberski, J.T., Z.H. Griebenow, R.M.M. Adams, A. Andersen, J. Andrade-Silva, P. Barden, M. Borowiec, S. Brady, S. Csősz, A.M. Dias, R.K.S. Dias, R.M. Feitosa, F. Fernandez, A. Casadei-Ferreira, B.L. Fisher, D.E.M. General, K. Gomez, M. Janda, A. Khalife, N. Ladino, Z. Lieberman, M. Menchetti, L. Pires do Prado, R.S. Probst, A. Punnath, A. Richter, R.R. Silva, S. Salata, A.F. Sánchez-Restrepo, E. Schifani, T.R. Schultz, J. Sosa-Calvo, M.C. Tocora, M.A. Ulysséa, W. Wang, J. Williams, G.P. Camacho, B.E. Boudinot. (in press, coming soon!). Ant Systematics: Past, Present and Future. Insect Systematics and Diversity.
• Redford, K.H.; Taber, A.; Simonetti, J.A. 1990. There is more to biodiversity than the tropical rain forests. Conservation Biology 4: 328–330. https://doi.org/10.1111/j.1523-1739.1990.tb00296.x
• Snelling, R. R. (1995). Systematics of Nearctic ants of the genus Dorymyrmex (Hymenoptera: Formicidae). Contributions in Science (Los Angeles), 454, 1–14. https://antcat.org/references/128901
• Trager, J. C. (1988). A revision of Conomyrma (Hymenoptera: Formicidae) from the southeastern United States, especially Florida, with keys to the species. The Florida Entomologist, 71(1), 11–29. https://doi.org/10.2307/3494888
• Young, A.D.; Gillung, J.P. 2020. Phylogenomics — principles, opportunities and pitfalls of big-data phylogenetics. Systematic Entomology 45: 225–247. https://doi.org/10.1111/syen.12406